Research Of Doppler Tei Index Based Evaluation For Cardiac Resynchronization Therapy Of Chronic Heart Failure Patients

Background and objective:Patients with symptomatic heart failure secondary to nonischemic cardiomyopathy or ischemic cardiomyopathy frequently exhibit intraventricular conduction delay that is thought to indicate dyssynchronous ventricular contraction and associated compromised hemodynamic performance. Cardiac synchronization therapy (CRT) has become an important therapy for patients with congestive heart failure and a widened QRS duration who remain symptomatic despite optimal medical therapy. Many studies have demonstrated that CRT not only improves hemodynamic performance but also results in improved symptom status, exercise capacity, and prognosis. The Tei index, defined as the sum of the isovolumic contraction and relaxation times divided by the ejection time (ET), is a quantitative measure of global ventricular function that permits noninvasive prognostic assessment of patients with cardiac amyloidosis, dilated cardiomyopathy, myocardial infarction (left ventricular [LV] dysfunction), and primary pulmonary hypertension (right [RV] ventricular dysfunction). Patients with systolic heart failure and intraventricular conduction delay have prolongation of the isovolumic periods; thus, the Tei index is prolonged, but the impact of CRT on these time periods has not been fully explored. Moreover, it would be of clinical interest to correlate the overall functional response to CRT with changes in these isovolumic periods. The aim of this study was to evaluate the effect of CRT on LV and RV Tei index at7day and6months after biventricular pacing compared with baseline (before CRT), specifically comparing responders to CRT with nonresponders.Between June2009and July2011,36patients with heart failure who underwent clinically indicated CRT at Zhejiang Hospital, were enrolled if they met the following inclusion criteria:1) LV systolic dysfunction; LV ejection fraction (LVEF) less than35%;2) New York Heart Association (NYHA) class3to4heart failure; and3) QRS width120ms or more. Patients with atrial fibrillation or frequent ventricular ectopy (>15ectopic beats/min) were not included because of the inability to consistently measure the parameters necessary to derive the Tei index. At the time of CRT device implantation, all patients were receiving optimal medications, including beta-blockers, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, spironolactone, and loop diuretics. Twenty two patients had nonischemic cardiomyopathy, and fourteen patients had an ischemic cardiomyopathy with a history of myocardial infarction. Standard2-dimensional and Doppler echocardiographic examinations were performed using a Vivid7echocardiographic machine(GE Medical Systems) before biventricular pacing and at7day and follow-up (6months) after CRT. LV volume and LVEF were calculated using the apical4-and2-chamber views(biplane Simpson’s method). LV diastolic function was assessed by pulsed-wave Doppler echocardiography of mitral inflow velocity and tissue Doppler echocardiography of mitral septal annular velocity.Right ventricular systolic pressure (RVSP) was derived from the tricuspid regurgitation velocity and an estimate of the right atrial pressure based on the dimension of inferior vena cava.Results:The Tei index decreased7day after CRT (left ventricle [LV]:P>.001, right ventricle [RV]:P>0.01) and remained lower at follow-up (LV and RV:P<.001vs baseline). Responders had a higher LV Tei index at baseline and achieved a sustained improvement in Tei index at follow-up (LV:P<.001) in contrast with nonresponders (LV and RV:not significant). Baseline LV Tei index and change in LV Tei index were both correlated with LV end-systolic volume reduction after CRT.Conclusion:Our observations describe the changes in echocardiographic parameters including the Doppler Tei index before and7day and6months after CRT, and suggest the potential clinical value of the baseline Tei index as a predictor of CRT response. The LV Tei index shows sustained improvement in responders to CRT. Although improvement occurs in nonresponders, this is not sustained. Responders also display a larger baseline LV Tei index compared with nonresponders, presumably because legitimate dyssynchrony prolongs the isovolumic contraction interval. The RV Tei index also improves significantly in responders to CRT, although to a lesser degree than the improvement in LV Tei index. This benefit of CRT to RV function in responders may result from the observed improvement in LV function.